scholarly journals Intercellular Communication within the Rat Anterior Pituitary Gland. XV. Properties of Spontaneous and LHRH-Induced Ca2+ Transients in the Transitional Zone of the Rat Anterior Pituitary in Situ

Endocrinology ◽  
2013 ◽  
Vol 154 (1) ◽  
pp. 400-409 ◽  
Author(s):  
Kazuki Hattori ◽  
Nobuyuki Shirasawa ◽  
Hikaru Suzuki ◽  
Takanobu Otsuka ◽  
Ikuo Wada ◽  
...  
Keyword(s):  
Anterior Pituitary ◽  
Cyclopiazonic Acid ◽  
Transitional Zone ◽  
Neonatal Rat ◽  
Neonatal Rats ◽  
Adult Rats ◽  
Adult Rat ◽  
Voltage Dependent

In the transitional zone of the rat anterior pituitary, spontaneous and LHRH-induced Ca2+ dynamics were visualized using fluo-4 fluorescence Ca2+ imaging. A majority of cells exhibited spontaneous Ca2+ transients, while small populations of cells remained quiescent. Approximately 70% of spontaneously active cells generated fast, oscillatory Ca2+ transients that were inhibited by cyclopiazonic acid (10 μm) but not nicardipine (1 μm), suggesting that Ca2+ handling by endoplasmic reticulum, but not Ca2+ influx through voltage-dependent L-type Ca2+ channels, plays a fundamental role in their generation. In the adult rat anterior pituitary, LHRH (100 μg/ml) caused a transient increase in the Ca2+ level in a majority of preparations taken from the morning group rats killed between 0930 h and 1030 h. However, the second application of LHRH invariably failed to elevate Ca2+ levels, suggesting that the long-lasting refractoriness to LHRH stimulation was developed upon the first challenge of LHRH. In contrast, LHRH had no effect in most preparations taken from the afternoon group rats euthanized between 1200 h and 1400 h. In the neonatal rat anterior pituitary, LHRH caused a suppression of spontaneous Ca2+ transients. Strikingly, the second application of LHRH was capable of reproducing the suppression of Ca2+ signals, indicating that the refractoriness to LHRH had not been established in neonatal rats. These results suggest that responsiveness to LHRH has a long-term refractoriness in adult rats, and that the physiological LHRH surge may be clocked in the morning. Moreover, LHRH-induced excitation and associated refractoriness appear to be incomplete in neonatal rats and may be acquired during development.

Stimulation at 1-5 Hz does not produce long-term depression or depotentiation in the hippocampus of the adult rat in vivo

1995 ◽  
Vol 74 (4) ◽  
pp. 1793-1799 ◽  
Author(s):  
M. L. Errington ◽  
T. V. Bliss ◽  
G. Richter-Levin ◽  
K. Yenk ◽  
V. Doyere ◽  
...  
Keyword(s):  
Young Animal ◽  
Low Frequency ◽  
Long Term Depression ◽  
Developmentally Regulated ◽  
Adult Rats ◽  
Adult Rat ◽  
Area Ca1 ◽  
Awake Rat

1. We examined the efficacy of low-frequency trains (1-5 Hz) in producing long-term depression (LTD) or depotentiation in the hippocampus of the awake adult rat and in anesthetized rats aged from 10 days to 3 mo. 2. In the dentate gyrus we found no evidence that low-frequency trains produce either depotentiation or LTD in the awake, adult animal or in the anesthetized animal at any age tested (10 days-adult). 3. In area CA1 of both awake and anesthetized adult rats, we also found no evidence that low-frequency trains induced either LTD or depotentiation. Only in area CA1 of very young rats (10-11 days) was clear evidence for LTD and depotentiation obtained; at this age experiments were only possible in anesthetized animals. By 16 days, the ability to display both LTD and depotentiation was lost. 4. These experiments suggest that repetitive low-frequency stimulation evokes a developmentally regulated form of activity-dependent depression that in the hippocampus is limited to specific pathways in the young animal. Our results leave open the question of whether alternative patterns of activity can induce LTD and/or depotentiation in the adult awake rat.

scholarly journals Cryopreserved ovarian tissues can maintain a long-term function after heterotopic autotransplantation in rat

Reproduction ◽  
2009 ◽  
Vol 138 (3) ◽  
pp. 519-525 ◽  
Author(s):  
Xiaohui Deng ◽  
Hua Zheng ◽  
Xuan Yu ◽  
Hongling Yu ◽  
Chengmei Zhang ◽  
...  
Keyword(s):  
Reproductive Tract ◽  
Ovarian Function ◽  
Hormone Secretion ◽  
Endocrine Function ◽  
Heterotopic Transplantation ◽  
Adult Rats ◽  
Primordial Follicles ◽  
Time Points ◽  
Adult Rat

The functional longevity of cryopreserved ovarian grafts is one of the most challenging questions regarding ovarian transplantation at present. This study used a rat ovarian grafting model to investigate whether ovarian tissues from adult rats, which had been cryopreserved by vitrification and followed by heterotopic transplantation, could establish long-term hormone secretion and follicle development. Fresh and cryopreserved ovarian tissues were autologously transplanted under the kidney capsule. One-third of the animals in each group (sham-operated, fresh autografts, cryopreserved autografts, or castrated) were killed 5, 8, or 10 months after transplantation. Vaginal cytology, serum estradiol (E2), progesterone, and the morphology of the reproductive tract were used to assess ovarian function. Both fresh and cryopreserved ovarian grafts survived well in all the animal models with comparable proportion of follicles at each stage of folliculogenesis at all three time points. The serum E2 and progesterone concentrations in the groups with fresh or cryopreserved grafts remained comparable with those in sham-operated controls at all investigated time points. However, a loss of grafts and primordial follicles following heterotopic transplantation was noted. In conclusion, the heterotopic autotransplantation of vitrified ovarian tissues from adult rat without vascular anastomosis can maintain long-term ovarian function and exert endocrine function in target organs, in spite of the reduction in follicle pool.

Calcium Release From Internal Stores Is Required for the Generation of Spontaneous Hyperpolarizations in Dopaminergic Neurons of Neonatal Rats

2000 ◽  
Vol 83 (1) ◽  
pp. 192-197 ◽  
Author(s):  
Vincent Seutin ◽  
Fatiha Mkahli ◽  
Laurent Massotte ◽  
Albert Dresse
Keyword(s):  
Dopaminergic Neurons ◽  
Calcium Release ◽  
Striated Muscle ◽  
Specific Inhibitor ◽  
Cyclopiazonic Acid ◽  
The Other ◽  
Neonatal Rats ◽  
Adult Rats ◽  
Voltage Gated ◽  
Midbrain Dopaminergic Neurons

We recently have demonstrated the existence of spontaneous hyperpolarizations in midbrain dopaminergic neurons of neonatal but not adult rats. These events are mediated by the opening of apamin-sensitive K+ channels after a rise in the intracellular concentration of Ca2+. They are resistant to tetrodotoxin in most cases and are probably endogenous (i.e., not synaptically activated). Here their mechanism was investigated. Cyclopiazonic acid (10 μM), a specific inhibitor of endoplasmic reticulum Ca2+ ATPases, reversibly abolished the events. Caffeine, which promotes Ca2+ release from intracellular stores, had concentration-dependent effects. At 1 mM, it markedly and steadily increased the frequency and the amplitude of the hyperpolarizations. At 10 mM, it induced a transient increase in their frequency followed by their cessation. All these effects were quickly reversible. Ryanodine (10 μM), which decreases the conductance of Ca2+ release channels, irreversibly blocked the spontaneous hyperpolarizations. Dantrolene (100 μM), a blocker of Ca2+ release from sarcoplasmic reticulum of striated muscle, did not affect the events. On the other hand, Cd2+(100–300 μM), a broad antagonist of membrane voltage-gated Ca2+ channels, significantly reduced the amplitude and the frequency of the hyperpolarizations. However, when the frequency of the events was increased by 1 mM caffeine, Cd2+ affected them to a smaller extent, whereas cyclopiazonic acid still abolished them. We conclude that internal stores are the major source of Ca2+ ions that induce the K+ channel openings underlying the spontaneous hyperpolarizations of these neurons.

Characterization of Mitotic Neurons Derived From Adult Rat Hypothalamus and Brain Stem

2002 ◽  
Vol 87 (2) ◽  
pp. 1076-1085 ◽  
Author(s):  
Jenafer Evans ◽  
Colin Sumners ◽  
Jennifer Moore ◽  
Matthew J. Huentelman ◽  
Jie Deng ◽  
...  
Keyword(s):  
Tissue Culture ◽  
Membrane Potential ◽  
Brain Stem ◽  
Adult Brain ◽  
Neonatal Rat ◽  
Peak Current Density ◽  
Adult Rats ◽  
Peak Current ◽  
Rat Hypothalamus ◽  
Adult Rat

Embryonic or neonatal rat neurons retain plasticity and are readily grown in tissue culture, but neurons of the adult brain were thought to be terminally differentiated and therefore difficult to culture. Recent studies, however, suggest that it may be possible to culture differentiated neurons from the hippocampus of adult rats. We modified these procedures to grow differentiated neurons from adult rat hypothalamus and brain stem. At day 7 in tissue culture and beyond, the predominant cell types in hypothalamic and brain stem cultures had a stellate morphology and could be subdivided into two distinct groups, one of which stained with antibodies to the immature neuron marker α-internexin, while the other stained with the astrocyte marker GFAP. The α-internexin positive cells were mitotic and grew to form a characteristic two-dimensional cellular network. These α-internexin positive cells coimmunostained for the neuronal markers MAP2, type III β-tubulin, and tau, and also bound tetanus toxin, but were negative for the oligodendrocyte marker GalC and also for the neurofilament triplet proteins NF-L, NF-M, and NF-H, markers of more mature neurons. Patch-clamp analysis of these α-internexin positive cells revealed small Ca2+ currents with a peak current of −0.5 ± 0.1 pA/pF at a membrane potential of −20 mV ( n = 5) and half-maximal activation at −30 mV ( n = 5). Na+ currents with a peak current density of −154.5 ± 49.8 pA/pF at a membrane potential of −15 mV ( n = 5) were also present. We also show that these cells can be frozen and regrown in tissue culture and that they can be efficiently infected by viral vectors. These cells therefore have the immunological and electrophysiological properties of immature mitotic neurons and should be useful in a variety of future studies of neuronal differentiation and function.

scholarly journals Comparative analysis of neonatal and adult rat carotid body responses to chronic intermittent hypoxia

2008 ◽  
Vol 104 (5) ◽  
pp. 1287-1294 ◽  
Author(s):  
Anita Pawar ◽  
Ying-Jie Peng ◽  
Frank J. Jacono ◽  
Nanduri R. Prabhakar
Keyword(s):  
Carotid Body ◽  
Intermittent Hypoxia ◽  
Ex Vivo ◽  
Adult Life ◽  
Sensory Response ◽  
Chronic Intermittent Hypoxia ◽  
Adult Rats ◽  
Adult Rat ◽  
Carotid Bodies

Previous studies suggest that carotid body responses to long-term changes in environmental oxygen differ between neonates and adults. In the present study we tested the hypothesis that the effects of chronic intermittent hypoxia (CIH) on the carotid body differ between neonates and adult rats. Experiments were performed on neonatal (1–10 days) and adult (6–8 wk) males exposed either to CIH (9 episodes/h; 8 h/day) or to normoxia. Sensory activity was recorded from ex vivo carotid bodies. CIH augmented the hypoxic sensory response (HSR) in both groups. The magnitude of CIH-evoked hypoxic sensitization was significantly greater in neonates than in adults. Seventy-two episodes of CIH were sufficient to evoke hypoxic sensitization in neonates, whereas as many as 720 CIH episodes were required in adults, suggesting that neonatal carotid bodies are more sensitive to CIH than adult carotid bodies. CIH-induced hypoxic sensitization was reversed in adult rats after reexposure to 10 days of normoxia, whereas the effects of neonatal CIH persisted into adult life (2 mo). Acute intermittent hypoxia (IH) evoked sensory long-term facilitation of the carotid body activity (sensory LTF, i.e., increased baseline neural activity following acute IH) in CIH-exposed adults but not in neonates. The effects of CIH were associated with hyperplasia of glomus cells in neonatal but not in adult carotid bodies. These observations demonstrate that responses to CIH differ between neonates and adults with regard to the magnitude of sensitization of HSR, susceptibility to CIH, induction of sensory LTF, reversibility of the responses, and morphological remodeling of the chemoreceptor tissue.

Calcium exchange, structure, and function in cultured adult myocardial cells

1987 ◽  
Vol 252 (2) ◽  
pp. H314-H324 ◽  
Author(s):  
G. A. Langer ◽  
J. S. Frank ◽  
T. L. Rich ◽  
F. B. Orner
Keyword(s):  
Rat Heart ◽  
Neonatal Rat ◽  
Adult Rat ◽  
Ec Coupling ◽  
Exchange Structure ◽  
Ethanesulfonic Acid ◽  
And Function ◽  
Cellular Ca ◽  
Adult Cells

Cells digested from adult rat heart and cultured for 14 days demonstrate all the structural elements, in mature form, associated with the process of excitation-contraction (EC) coupling. The transverase tubular (TT) system is well developed with an extensive junctional sarcoplasmic reticulum (JSR). In nonphosphate-containing buffer contraction of the cells is lost as rapidly as zero extracellular Ca concentration ([Ca]o) solution is applied (less than 10 s) and a negative contraction staircase is produced on increase of stimulation frequency. Structurally and functionally the cells have the characteristics of adult cells in situ. 45Ca exchange and total 45Ca measurement in N-2-hydroxyethylpiperazine N'-2-ethanesulfonic acid (HEPES)-buffered perfusate define three components of cellular Ca: a rapidly exchangeable component (t1/2 less than 25 s) accounting for 36% of total Ca, a slowly exchangeable component (t1/2 53 min) accounting for 7% of total Ca, and the remaining 57% cellular Ca is “inexchangeable” (demonstrates no significant exchange within 60 min). The slowly exchangeable component can be increased 10-fold within 60 min by addition of phosphate to the perfusate. The Ca distribution and exchange characteristics are little different from those of 3-day cultures of neonatal rat heart previously studied [Langer, G. A., J. S. Frank, and L. M. Nudd. Am. J. Physiol. 237 (Heart Circ. Physiol. 6): H239-H246, 1979]. The results suggest that the cells are representative of adult cells in situ and that both sarcolemmal-bound and sarcoplasmic reticular Ca contribute to the component of Ca that is rapidly exchangeable.

Investigation of the potential role of the germ cell complement in control of the expression of transferrin mRNA in the prepubertal and adult rat testis

1997 ◽  
Vol 19 (1) ◽  
pp. 67-77 ◽  
Author(s):  
S M Maguire ◽  
M R Millar ◽  
R M Sharpe ◽  
J Gaughan ◽  
P T K Saunders
Keyword(s):  
Germ Cell ◽  
Mrna Expression ◽  
Germ Cells ◽  
Sertoli Cells ◽  
Direct Access ◽  
Adult Rats ◽  
Rat Testis ◽  
Adult Rat

ABSTRACT Iron is required for the normal development of germ cells during spermatogenesis. Because these cells have no direct access to systemic iron, there exists a shuttle system involving production and secretion of the iron-transporting protein transferrin by the Sertoli cells. Previous reports using cultures of immature Sertoli cells exposed to adult germ cells, or in vivo studies involving germ cell-depleted adult rat testes, concluded that production of transferrin by Sertoli cells is modulated by germ cell complement. In the present study we have used in situ hybridisation with cRNA probes directed against the 5′ and 3′ ends of transferrin mRNA to examine the pattern of expression of transferrin in the immature and adult rat testis. Adult rats were treated with ethane dimethane sulphonate or methoxyacetic acid (MAA) to manipulate their testosterone levels or germ cell complement respectively. Initial findings obtained using the 3′ probe showed a decrease in transferrin mRNA associated with round spermatid depletion. However, these data were not confirmed by in situ hybridisation when the 5′ probe was used. The specificity of the probes was examined using Northern blotting and the 3′ probe was found to hybridise to the germ cell transcript for hemiferrin even under conditions of high stringency. Examination of immature and pubertal rat testes by in situ hybridisation using the 5′ transferrin-specific probe found that as early as 14 days of age the level of expression of transferrin mRNA was clearly different between tubules, and the mRNA appeared to be expressed in Leydig cells on and after day 31. In the adult rat testis, maximal expression of transferrin mRNA was found at stages VIII-XIV, calling into question the interpretation of the results of some previous studies showing expression of transferrin mRNA at all stages of the spermatogenic cycle. This stage-specific pattern of expression was not altered by acute germ cell depletion using MAA. However, Northern blot analysis showed a statistically significant increase in transferrin mRNA expression at 7 days after MAA treatment when pachytene spermatocytes were depleted from tubules at all stages of the spermatogenic cycle at which transferrin is normally expressed. In conclusion, we found that transferrin mRNA expression was not modulated by round spermatids as has been reported previously but that meiotic germ cells may influence expression of transferrin at specific stages of the spermatogenic cycle.

scholarly journals Immunoreactive erythropoietin concentrations in fetal and neonatal rats and the effects of hypoxia

Blood ◽  
1986 ◽  
Vol 68 (4) ◽  
pp. 892-899 ◽  
Author(s):  
GK Clemons ◽  
SL Fitzsimmons ◽  
D DeManincor
Keyword(s):  
Rat Plasma ◽  
Neonatal Rat ◽  
Control Group ◽  
Neonatal Rats ◽  
Rat Fetus ◽  
Female Response ◽  
Adult Rat ◽  
Hypoxic Conditions ◽  
Fetal Rats ◽  
Maternal Hypoxia

Immunoreactive erythropoietin (Ep) was measured in normoxic and hypoxic (0.5 atm; 18 hours) fetal rats from day 14 to day 21 of gestation and in neonatal rats from birth to weaning, and was compared to the adult rat. Amniotic fluid (AF) Ep was approximately 100 mU/mL on day 14 and 15, and decreased to 20 mU/mL on day 20, with no difference between the hypoxic and normoxic mothers. Only on day 21 did the Ep in the AF increase slightly in the hypoxic group, while the Ep in the control group continued to fall to 15 mU/mL on day 21, the last day of pregnancy. Before day 17 of gestation the rat fetus appears to have hypoxia-independent, extrahepatic Ep available which is followed by hepatic and renal Ep production, both of which become sensitive to maternal hypoxia during the last days of pregnancy. In the neonatal rat plasma and tissue, Ep levels varied greatly during the first three weeks of life regardless of whether the animals were hypoxic or not. With the exception of the first and ninth days of life, circulating Ep levels were higher than adult levels in normal newborn rats. Neonatal rats responded to hypoxia with increasing Ep levels, and the response increased with age such that during the third week of life the plasma Ep levels were significantly higher than in adult hypoxic rats. No sex difference in male and female response to hypoxia could be documented until sexual maturity (day 42). In the normoxic neonatal rat more Ep originated from the liver than the kidneys until day 10, while under hypoxic conditions the switch occurred as early as two days after birth.

Effect of strontium on the contractile properties of postnatally developing rat heart ventricles

1985 ◽  
Vol 63 (1) ◽  
pp. 9-17 ◽  
Author(s):  
Matti Vornanen
Keyword(s):  
Rat Heart ◽  
Age Groups ◽  
Contractile Properties ◽  
Neonatal Rat ◽  
Calcium Stores ◽  
Adult Rats ◽  
Adult Rat ◽  
Twitch Potentiation ◽  
Developing Rat ◽  
T System

The effects of substitution of calcium (Ca) by an equimolar concentration of strontium (Sr) on isometric contractions of isolated ventricular muscle from postnatally developing rat heart were studied. The duration of contraction and the time-to-peak tension were increased in all age groups although much less in the adult rats than in the neonates. The contractile force was increased in the muscles of rats between 1 and 14 days of age but was depressed in the older animals. The prominent rest-twitch potentiation of neonatal rat heart in Ca− Tyrode was totally eliminated by Sr, whereas a clear rest-twitch potentiation was induced by this cation in the adult rat heart, in which tissue the potentiation is normally absent in Ca− Tyrode. The maximal twitch potentiation by rest in Ca− Tyrode and the positive inotropic effect of Sr substitution grew from birth up to day 9 and from then gradually declined towards the level of adult rat heart by the end of the 3rd postnatal week. The phase of increasing rest-twitch potentiation coincides fairly well with the known development of sarcoplasmic reticulum and the phase of decline with the appearance of the T system of the sarcolemma. It is suggested that the qualitative changes in the contractile properties of developing rat heart during the 3rd postnatal week are due to the more efficient utilization of intracellular calcium stores, owing to the development of the T system.

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